DIGESTION AND ABSORPTION IN THE INTESTINES. 701 



of the secretion are formed they are frequently designated as zymogen 

 granules. The pancreas contains also certain peculiar groups of 

 cells, the islands (or bodies) of Langerhans. These cells have noth- 

 ing to do with the digestive activity of the pancreas. Their function 

 is referred to in the sections on internal secretions and nutrition. 



Composition of the Secretion. The pancreatic secretion is an 

 alkaline liquid which in some animals is thin and limpid, in others 

 thick and glairy. The secretion in man belongs to the former 

 type; it is described as water-clear and as having a specific gravity of 

 1.0075. The secretion may be collected by opening the abdomen 

 and inserting a cannula directly into the duct, or a permanent 

 fistula may be made by the method of Pawlow. This method, 

 applicable to the dog, consists in cutting out a small portion of 

 the duodenum where the pancreatic duct opens and then suturing 

 this piece, with mucous membrane outward, into the abdominal 

 wall. The secretion in this case pours out upon the exterior and may 

 be collected. The animal, however, suffers nutritive disturbances 

 from the loss of the secretion, and requires careful dieting and atten- 

 tion. The secretion of the human pancreas has been collected in a 

 single case* in which for a few days it was necessary to drain off the 

 pancreatic juice to the exterior. From the observations made in this 

 case it appears that the secretion in man is quite abundant, amount- 

 ing to 500 to 800 c.c. per day. In the cow (Delezenne) from 1J to 2 

 liters may be collected in the course of a day. The secretion possesses 

 a strong alkaline reaction, due to the presence of sodium carbonate; 

 it contains also a small amount of coagulable proteid and a number 

 of organic substances in traces. The important constituents,, how- 

 ever, are three enzymes or their zymogens, namely, trypsin, a 

 proteolytic enzyme; pancreatic diastase (amylopsin), an amylolytic 

 enzyme; and lipase (steapsin), a lipolytic enzyme. Some authors 

 state, also, that the secretion contains a rennin enzyme. Glaessner 

 reports that he got no evidence of this last enzyme in human pan- 

 creatic juice. 



Secretory Nerve Fibers to the Pancreas. The pancreas 

 receives its nerve supply immediately from the celiac plexus, but 

 stimulation of the nerves going to this plexus namely, the splanch- 

 nics and the vagi gave negative results in the hands of most 

 observers so far as the pancreatic secretion was concerned. Pawlowf 

 and his coworkers, however, have been more successful. Mechanical 

 stimulation or electrical stimulation of the vagus or splanchnic gave 

 them a marked flow of pancreatic juice, but when the latter form of 



* See Glaessner, " Zeitschrift f. physiol. Chemie, " 40, 465, 1903. 



t For recent work upon the pancreas and the literature see Pawlow, 

 "The Work of the Digestive Glands," translation by Thompson, 1902; Bay- 

 liss and Starling, "Journal of Physiology," 30, 61, 1904; Walter, "Archives 

 des sciences biologiques, " 7, 1, 1899. 



